Optimizing Higgs factories by modifying the recoil mass

It is difficult to measure the m WW-fusion Higgs production process (e⁺e^-→ννh) at a lepton collider with a center of mass energy of 240-250GeV due to its small rate and the large background from the Higgsstrahlung process with an invisible Z (e⁺e^-→hZ,Z→νν). We construct a modified recoil mass variable, m_recoil^p, defined using only the 3-momentum of the reconstructed Higgs particle, and show that it can separate the m WW-fusion and Higgsstrahlung events better than the original recoil mass variable m_recoil. Consequently, the m_recoil^p variable can be used to improve the overall precisions of the extracted Higgs couplings, in both the conventional framework and the effective-field-theory framework. We also explore the application of the m_recoil^p variable in the inclusive cross section measurements of the Higgsstrahlung process, while a quantitive analysis is left for future studies.